This application claims priority under 35 USC xc2xa7 119 to Japanese Patent Application Nos. 2001-222186, 2001-167346, and 2001-261814 filed on Jul. 23, 2001, Jun. 1, 2001, Aug. 30, 2001, respectively, the entire contents of which are herein incorporated by reference.
1 Field of the Invention
The present invention relates to a fixing apparatus and an image forming apparatus including a heat fixing member and a pressure applying member pressure contacting the fixing member.
In particular, the present invention relates to a fixing apparatus and image forming apparatus capable of fixing a toner image to a recording member while directing and conveying the recording member to and through a nip formed between the fixing member and pressure applying member in such a manner that the toner image contacts the fixing member.
2. Discussion of the Background
It has been well known that a fixing apparatus of the above-described type is adopted in an image forming apparatus, such as a copier, a printer, a facsimile, a combined machine having at least one of them, and etc. In such a type of the fixing apparatus, since the toner fuses when passing the nip formed between the fixing and pressure applying members, the toner likely functions as adhesive agent and the recording member ejected from the nip is not separated and wraps around the surface of the fixing member. In particular, in an image forming apparatus farming a full-color image, since different color toner images are superimposed on a recording member and fixed by a fixing apparatus, a plenty of toner necessarily fuses in the nip, and thus adhesive force of the toner increases. As a result, the recording member more readily wraps around the fixing member.
Then, in the past, a separation member including a plurality of separation claws is configured to contact a surface of a fixing member and separate a recording member ejected from a nip from the surface of the fixing member in order for the recording member not to wrap around the surface of the fixing member. However, since the separation claw contacts the surface of the fixing member via its tip, the surface likely is cut (e.g, damaged). As a result, a mark appears on a toner image after passing through the nip in accordance with the cut, and resulting in inferior toner image quality as a result of fixing.
To remove such a disadvantage, a fixing apparatus is proposed to arrange a separation claw separating from a surface of the fixing member. However, a recording member ejected from the nip likely enters into a gap formed between the fixing member and separation claw while sticking the surface of the fixing member. As a result, a separation function of the recording member is weakened and wrapping likelihood of the recording member around the fixing member increases.
In addition, there exists a case when a fixed toner image is formed on a backside surface of the recording member carrying a toner image on the other side to be fixed. In such a situation, since the toner image on the backside surface is fused by heat while passing through the nip, the recording member likely wraps around the surface of the pressure applying member. To avoid such a problem, a separation claw preferably contacts the surface of the pressure applying member. However, a similar problem arises as described in the above.
The present invention has been made in view of such problems and to address and resolve such problems. Accordingly, it is an object of the present invention to provide a novel fixing apparatus including a fixing member and a pressure applying member configured to pressure contact the fixing member. The fixing apparatus directs and conveys a recording member through a nip formed between the fixing member and pressure applying member so that a toner image carried on the recording member can contact the fixing member to be fixed thereto with heat and pressure. The fixing apparatus is configured to direct a margin formed in a transfer direction tip of the recording member across a virtual linear extension line drawn from a downstream end to an upstream end both in the nip toward the pressure applying member, when only the margin exits from the nip. A fixing member side separation device is provided so as to separate the recording member ejected from the nip not contacting the surface of the fixing apparatus. In addition, a gap between the downstream end of the nip and the tip of the fixing member side separation device is set smaller than the width of the margin of the downstream end.
In yet another embodiment, a JIS-A (Asker-C) hardness of the surface of the pressure applying member of the nip at the downstream end may be larger than that of the downstream end of the fixing member.
In another embodiment, a pressure applying member side separation device is provided with its tip contacting the surface of the pressure applying member.
In yet another embodiment, a JIS-A hardness of the surface of the fixing member in the nip in the downstream end is substantially the same to that of the downstream end of the surface of the pressure applying member.
In yet another embodiment, a JIS-A hardness of the surface of the fixing member of the nip in the downstream end is higher than that of the downstream end of the pressure applying member.
In yet another embodiment, a fixing member side separation device is provided with its tip contacting the surface of the fixing member.
In yet another embodiment, gap maintaining members are provided on respective tips of the fixing member side separation devices disposed in a direction perpendicular to the transfer direction so as to contact the surface of a non-transfer member passage area of the fixing member so that a gap formed between the tip of the fixing member side separation device and the surface of the fixing member is maintained.
In yet another embodiment, gap maintaining members are also provided on respective tips of the pressure applying member side separation devices so as to contact the surface of a non-transfer member passage area of the pressure applying member so that a gap formed between the tip of the pressure applying member side separation device and the surface of the pressure applying member is maintained.
In yet another embodiment, the fixing member side separation device is a single separation member type.
In yet another embodiment, the pressure applying member side separation device is a single separation member type.
In yet another embodiment, the fixing member side separation device includes an opening for ventilation.
In yet another embodiment; the pressure applying member side separation device includes an opening for ventilation.
In yet another embodiment, the fixing member side separation device is formed from a sheet like separation member, and is biased by a tension applying member in a direction perpendicular to the transfer direction.
In yet another embodiment, the pressure applying member side separation device is formed from a sheet like separation member, and is biased be a tension applying member in a direction perpendicular to the transfer direction.
In yet another embodiment, toner includes, at least, plastic, colorant, and wax.